I personally don't think it's Joff-Adis trusted him, his wife and child were killed and he clearly loved them (the way things were presented made it feel like the Enthrallers targeted extreme hatreds first), and, well, he was a Fire type. While normally I wouldn't exclude by type or form, a fire type meant it would be extremely dangerous to just fall in the lake.

So, it's either the Flaffy Teacher (unliekly as Adis trusted her), Dami or the Swellow mother...And none of the DNA samples had down or feathers in them. Unless birds have legit fur, which I'd be confused at, it cannot be an Avian Pokemon. So Nashelle is out.

To be on the safe side, let's interview as many of them as possible on the school-before and after the Stalkers, mind. Non is related to the school absolutely and for certain, or at least children-that much is absolutely certain.